People who are 30 pounds or more overweight may want to slim down a bit even if they don’t have high blood pressure or any other heart disease risk, according to scientists at Wake Forest Baptist Medical Center.

In a study published in the May issue of the Journal of the American College of Cardiology, the researchers found that slightly less than half of the people who were considered obese—30 pounds or more overweight—developed metabolic syndrome within 10 years, putting them at a much higher risk for cardiovascular disease and diabetes.

“Common medical wisdom has been that some people who are obese seemed to be pretty healthy and free from heart disease risks, so they haven’t been advised to lose weight or take other steps to prevent future heart disease,” said Morgana Mongraw-Chaffin, PhD, assistant professor of public health sciences at Wake Forest Baptist and lead author of the study.

“The big question has been whether these people who are metabolically healthy will stay that way or whether they will progress to metabolic syndrome over time.”

Metabolic syndrome includes those risk factors—high blood pressure, high blood sugar, unhealthy cholesterol levels, and abdominal fat—which double the risk of cardiovascular disease that can lead to heart attacks and strokes. In addition, these risk factors increase the risk of diabetes by five times.

The Wake Forest Baptist study included 6,809 participants from the Multi-Ethnic Study of Atherosclerosis who were recruited from six sites in the United States. Participants with cardiovascular disease were excluded.

The study was conducted to determine if metabolically healthy obesity (MHO) at baseline remained stable or led to metabolic syndrome and increased the risk of heart and vascular disease. Participants were followed for 12 years with clinical evaluation repeated every 2 years. MHO was defined as a BMI of more than 30 and two or fewer risk factors.

The researchers found that compared to normal weight, baseline MHO was not significantly associated with incident cardiovascular disease, the first occurrence of a potentially life-threatening condition. However, almost half of the participants developed metabolic syndrome over the course of the study and had increased odds of cardiovascular disease compared to those with stable MHO and normal weight.

“In this paper, we specifically looked to see whether that progression was associated with a higher risk for heart disease and we found that it was,” Mongraw-Chaffin said. “MHO is not a stable or reliable indicator of future risk for cardiovascular disease. Right now, there isn’t any way to know which 50% will progress and which won’t.

“Therefore, we recommend that everyone with MHO work with their doctor to lose weight or at least maintain their current weight, exercise more, and make other lifestyle changes so they don’t develop metabolic syndrome.”